Segment-in-series cell fabricated by Mitsubishi Heavy Industries have been investigated from various experimental approaches. Examined samples are type 1 cells which were operated for up to 10,000 h by CRIEPI. Analyses were made by AIST on materials transport with dynamic SIMS, by CRIEPI on microstructure observation with EPMA, by Kyoto University on microstructure change with FIB-SEM, by Kyushu University on chemical states with S-TEM, and by Tohoku University on mechanical properties in the microscopic zone with micro indentation technique. On the bases of accumulated knowledge on these samples, the materials deterioration model has been established with a focus on the movement of the Ca component in the cathode layers. The degradation rate observed in the analyses by CRIEPI can be interpreted in terms of the Cr deposited on the three phase boundaries and also of the change in microstructure.